12v fuel mod

[UltraFlynn]

I almost 100% certain that the 12v fuel pump mod (http://www.mkiv.com/techarticles/12v_mod/12v_mod.htm) has been done to my car and I can always here the fuel pump whirring away.

My question is ..... is it really necessary on my car?

I know the benefits of having it done are that it's supposed to reduce the chance of detonation at about 4000rpm as that where the 2nd turbo comes online and also where the fuel pump goes into high pressure mode.

Does anyone else have this mod done?

[Martin F]

Yes its been done to mine, thanks :D

[UltraFlynn]

So it's something that I should in then is it?

[Martin F]

Well whether you need it or not is a bit hard to determine as the best way to tell would be to remove it and then have your fueling checked on a rolling road or similar.

However that being said there is no harm in having it fitted apart from the possible reduction in service life for the pump. Also its worth checking to make sure the conversion has been done properly as some people fit them so that the pump is constantly running when the ignition is on and that is potentially dangerous if you were ever involved in an accident. By making use of the output from the fuel pump ECU it will cut out the fuel pump if the engine is not running after a few seconds.

[UltraFlynn]

That'll be another thing to add to my long list of things to do then. :)

[Stephen Brownbridge]

Martin/Flynn,

My Supra has slight detonation when the second turbo kicks in under hard acceleration around 4000rpm; I plan to have the fuel mod done soon.

My car is a Jap Spec Auto. TT.

Any downsides or other points to take on board?

I run on Nippon Denso IK22 plugs and Shell V Power.

Regards

Stephen B

[Martin F]

I would say it is worth a try to see if it cures your problem. How do you know you have detonation?

As above the only downside is possibly a shortened pump life.

[Stephen Brownbridge]

Martin,

I think it is detonation as it is a very slight 'rattle' on full acceleration and was confirmed by Clive Atthowe tuning of Norwich who did my Dyno test (we didn't check the air fuel ration though).

I don't think it will do any harm to try the mod anyhow.

Cheers and Happy New Year all!!

Stephen B

[Storm]

Sure it's not pinking under load.
I doubt you would here detonation unless your car is on the rollers with your ear to the block. I wouldn,t decribe det as a rattle.
If it is detting then I,d be rather concerned as det will kill your pistons in milli seconds.
I was under the impression, stock supra,s over fuel so you must have some problems somewhere.
Im not knowledgable on the Supra so perhaps some of the more technical people on the forum can point you right.

[Martin F]

http://en.wikipedia.org/wiki/Engine_knocking

If you can hear detonation without the aid of a stethoscope, microphone etc, then it must be quite bad. You need to try and investigate it as soon as possible, and perhaps as an interim measure turn the boost down.

If you fit the 12v fuel mod and your car already has sufficient fuel at the switch over point, you will actually reduce your power (more fuel = less power beyond stoich).

Probably best to get another run done and have the air fuel ratio checked at the same time as this can also show up detonation.

[Stephen Brownbridge]

Martin/Storm,

Thanks for your input.

The sound is a 'Pinking' sound but very slight and only on 'foot to the floor' acceleration at about 4,000 rpm.

I am running 15lbs or 1.15 bar boost.

I will Dyno the car again and check the Fuel/Air ratio before looking to do the fuel pump mod.

Cheers

Stephen B

[Bob]

It may not be detonation at all - I had something similar when my 2nd turbo came online and it turned out to be a couple of duff coils.

[Nod]

DO NOT do the 12v mod. The Fuel pump ECU only runs at lower voltages at light load, when on boost it runs at near nbv+. I have lost count of the amount of 12v's MOD's I've had to repair in order to sort MK4 fueling issues out. You can tell if the mod has been done if the fuel pump is using 13+ volts @ idle (it should be about 10v). It is usually done at the fuel pump ecu which is behind the passenger rear boot panel near the shock tower (I believe there boot light is also in the same panel). The two fat wires of the 5 way plug are shorted together. (It's usually cut right at the plug so you have to depin it to repair it too which is a pain).

Nod.

[UltraFlynn]

My rather dodgy 12v mod is on the list of things to sort out. It will most likely be going back to standard.

[Stephen Brownbridge]

Bob,

I have been thinking at looking at replacing the Coil Packs as my car was based in the West Indies and the heat has a tendency to break down a lot of plastic bits over time but I have never experienced a missfire.

However at £95 a pop in the UK they are expensive; I may get them from the US as they are £200 for a set of 6!

Anyone else had coil pack replacement solving pinking/det issues?

Cheers

Stephen B